1. Technical Field
The present invention relates generally to an X-ray transmission inspection apparatus and an inspection method using the same, the apparatus and method being capable of detecting minute foreign matter in a sample. More particularly, the present invention relates to an X-ray transmission inspection apparatus and inspection method using the same, the apparatus and method being capable of detecting foreign matter smaller than tens of μm in size in a sample.
2. Description of the Related Art
Generally, to detect foreign matter, such as a minute metal particle, in a sample, X-ray transmission inspection is used on the sample by means of an X-ray transmission image that is obtained by irradiating a sample with X-rays. For example, in a lithium-ion secondary battery, which has been recently applied to an automobile, a hybrid vehicle, an electric vehicle, or the like, an electrode, as an anode, of the lithium-ion secondary battery is formed in such a manner that a lithium manganese oxide film or a lithium cobalt oxide film is formed on both surfaces of an Al film. Due to this, when foreign matter, such as Fe (iron) or SUS (stainless), having a size of tens of μm or larger is mixed into the battery, a short circuit may occur, causing a decrease in performance or even ignition of the battery. Therefore, there is a demand in the lithium-ion secondary battery that a battery with a foreign matter mixed therein during production be detected and removed in advance.
As an X-ray transmission inspection apparatus for detecting foreign matter or the like in a sample is well-known. In such an inspection apparatus, during inspection, an X-ray source and an X-ray detector, such as a line sensor, face each other, and a sample moving in one direction is disposed therebetween. As an example, patent document 1 discloses an X-ray inspection apparatus for detecting a foreign matter, the apparatus capable of detecting even minute foreign matter with high sensitivity using a time delay integration sensor (TDI sensor).
The X-ray inspection apparatus, which is mentioned above, includes: an X-ray image intensifier (image intensity amplifier: IIF); a TDI sensor performing the functions of synchronizing an X-ray transmission image moving on an imaging surface of the X-ray image intensifier with a charge transfer speed of the TDI sensor; enlarging an image photographed on an input screen of the X-ray image intensifier in accordance with a belt conveyor velocity V by an optical enlargement ratio b/a, which is calculated based on a distance b from the X-ray source to a foreign matter (in effect, to the belt conveyor) and a distance a from the X-ray source to the input screen of the X-ray image intensifier; and calculating a velocity V3, as a moving velocity of an image of the foreign matter created by the TDI sensor, by multiplying the conveyor belt velocity V, b/a, and the rest.
In other words, in the conventional X-ray inspection apparatus for detecting foreign matter, an optical enlargement ratio, which is calculated both by synchronizing a moving velocity of the sample with the charge transfer speed of the TDI sensor, and by a ratio of a predetermined distance (FOD) between from the X-ray source to the foreign matter (in effect, to a mounting surface of a belt conveyor) to a distance (FDD) from the X-ray source to the X-ray detector: FDD/FOD, is set as a correction factor.
The foregoing is intended merely to aid in the understanding of the background of the present invention, and is not intended to mean that the present invention falls within the purview of the related art that is already known to those skilled in the art.